Young American students take a variety of standardized tests. But the ways that students are educated so that they’ll do well on such tests presents a problem. The preparation increases what’s called crystallized knowledge: that’s factual information, such as ‘the capital of Texas is Austin.’ But the tests do not enhance what is referred to as fluid intelligence: the ability to think logically or theoretically. That’s according to a study in the journal Psychological Science.

Scientists analyzed test scores and IQs of almost 1,400 eighth-graders. They found that schoolwork could significantly raise students’ test scores, while having no effect on the ratings of their fluid intelligence scores…which are better indicators of memory capacity, thinking speed and the ability to solve abstract problems.

It’s been shown that high scores on standardized tests predict success on future exams like the SAT and Advanced Placement tests. But little is known about the effect of improving fluid intelligence. Still, the researchers note that crystallized intelligence is clearly important, since, for example, mathematics and comprehension are critical for later academic and employment success. Systems that increase fluid intelligence would therefore seem to be a good development—logically and theoretically.

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